A heat roller for a laser printer has a roller pipe, a resistive heat element accommodated in the roller pipe, an internal expanding pipe installed in the roller pipe which restricts the resistive heat element by pushing the resistive heat element toward the roller pipe, caps coupled to both end portions of the internal expanding pipe and provided with electrodes which supply a current to the resistive heat element, a gear coupled to any one of the caps, and a coupling unit which restricts at least one of the caps from slipping along the internal expanding pipe. The heat roller has the enhanced secure coupling between the internal expanding pipe, the roller pipe, the coil and the insulation layer. Accordingly, it is possible to prevent slip off and coil short circuit.